This invention relates to measurement of tension in a moving threadline, and more particularly, to a tensiometer having an even surface threadline guide.
The measurement and monitoring of the tension of a moving threadline is essential in many filament and yarn processing operations. U.S. Pat. No. 4,295,360 to Fountain discloses one device for measuring threadline tension that includes a threadline direction-changing guide mounted at one end of a strain sensing cantilever. The threadline guide is typical of other prior art tensiometer guides in that it includes a groove for containing and preventing the threadline from wandering longitudinally along the guide surface. Likewise, U.S. Pat. No. Re. 31,312 to Eddens discloses a tension monitoring device having a rotatable pulley with an annular groove for accepting strand material. However, the use of a grooved guide surface for containing a moving threadline has been found to be undesirable for several reasons. For example, confining a running threadline within a grooved guide relies on a certain baseline level of threadline tension in order to keep the threadline firmly positioned within the groove. However, tension of the threadline at the desired measurement location can be too low to utilize a grooved guide for accurate tension measurement while still maintaining normal process conditions.
It would be desirable to have an even surfaced guide over which the threadline could run because a threadline running in a groove may create increased friction versus a threadline running over a flat surface and, decrease the sensitivity level of the tensiometer.
One problem with replacing a grooved guide with a guide having an even surface is that a running threadline wanders longitudinally along an even surface of a guide resulting in different and erroneous readings by the tensiometer for any particular tension. Devices such as Fountain's referenced above, if fitted with an even guide surface, would measure, in addition to actual threadline tension, a tension which would vary with respect to the axial location of the threadline as it wandered along the guide surface.
Furthermore, it is highly desirable to provide a wide range of accurate tension capability without sacrificing sensitivity at low ranges of tension while maintaining structural stability against erroneous forces.